Editing Tracheid (section)

{{Short description|Component of Xylem}}
[[File:Podocarpoxylon mcgeei radial section with tracheids Torrey 1923 Plate10 fig18.png|thumb|220px|In radial section, two tracheids of a coniferous wood species are shown. A series of bordered [[Pit (botany)|pits]] are also appearing in each tracheid.]]
[[File:Tracheid of oak (from Marshall Ward).png|thumb|150px|A tracheid of [[oak]] shows [[Glossary of botanical terms#pit|pits]] along the walls. It has no [[Glossary of botanical terms#perforation plate|perforation plates]]. Angiosperms have both tracheids and vessel elements.<ref>{{citation |title=Atlas of Plant and Animal Histology |publisher=University of Vigo, Spain |author=Megías M, Molist P, Pombal MA. |url=http://mmegias.webs.uvigo.es/index.html |access-date=11 December 2024}}</ref>]]

A '''tracheid''' is a long and tapered [[Lignin|lignified]] cell in the [[xylem]] of [[Tracheophyta|vascular plants]]. It is a type of conductive cell called a tracheary element. [[Angiosperms]] also use another type of conductive cell, called [[vessel element]]s, to transport water through the xylem. The main functions of tracheid cells are to [[Transpiration|transport water and inorganic salts]], and to provide structural support for trees. There are often [[Pit (botany)|pits]] on the [[cell walls]] of tracheids, which allows for water flow between cells. Tracheids are dead at functional maturity and do not have a [[protoplast]]. The [[wood]] ([[softwood]]) of [[gymnosperm]]s such as pines and other [[conifer]]s is mainly composed of tracheids.<ref>{{Cite journal|last1=Cuny|first1=Henri E.|last2=Rathgeber|first2=Cyrille B. K.|last3=Frank|first3=David|last4=Fonti|first4=Patrick|last5=Fournier|first5=Meriem|date=2014|title=Kinetics of tracheid development explain conifer tree-ring structure|url=https://onlinelibrary.wiley.com/doi/abs/10.1111/nph.12871|journal=New Phytologist|language=en|volume=203|issue=4|pages=1231–1241|doi=10.1111/nph.12871|pmid=24890661|bibcode=2014NewPh.203.1231C |s2cid=22862428 |issn=1469-8137}}</ref> Tracheids are also the main conductive cells in the primary xylem of [[fern]]s.<ref name="Pittermann-2011">{{Cite journal|last1=Pittermann|first1=Jarmila|last2=Limm|first2=Emily|last3=Rico|first3=Christopher|last4=Christman|first4=Mairgareth A.|date=2011|title=Structure–function constraints of tracheid-based xylem: a comparison of conifers and ferns|journal=New Phytologist|language=en|volume=192|issue=2|pages=449–461|doi=10.1111/j.1469-8137.2011.03817.x|pmid=21749396|issn=1469-8137|doi-access=free|bibcode=2011NewPh.192..449P }}</ref>

The tracheid was first named by the German botanist Carl Gustav Sanio in 1863, from the German ''Tracheide''.<ref>{{Cite journal|last=Sanio|first=C.|year=1863|title=Vergleichende Untersuchungen über die Elementarorgane des Holzkörpers|journal=Bot. Zeitung|volume=21|pages=85–91; 93–98; 101–111|issn=2509-5420}}</ref>